17.beta.-Estradiol, Estra-1,3,5,(10)-triene-3,17.beta.-diol, is a naturally occurring estrogen in mammals which is formed by the ovary, placenta, testes and possibly the adrenal cortex. 17.beta.-Estradiol is reported to promote growth and increase feed utilization efficiency. However, estriol and estrone, the weakly estrogenic metabolites of 17.beta.-estradiol, were reported not to promote growth or increase feed utilization efficiency. Preston et al., J. Am. Sci., Vol. 46, No.2, 541 (1978).
Estriol, Estra-1,3,5(10)-triene-3,16.alpha.,17.beta.-triol, is a metabolite of 17.beta.-estradiol. Estriol has been isolated from: Urine as disclosed in Marrian, Biochem. J., 23:1233 (1929); Placenta as disclosed in Collip et al, Endocrinology, 18:71 (1934); and Plants as disclosed in Skarzynski, Nature, 131:766 (1933). Estriol's structure was disclosed in Huffman, et al., J. Am. Chem. Soc., 69:1835 (1947). Estriol is synthesized according to the methods disclosed in Huffman et al., J. Am. Chem. Soc., 71:719 (1940) and Leeds et al., J. Am. Chem. Soc., 76:2943 (1954).
U.S. Pat. No. 4,078,060 to Benson et al discloses using estrogen derivatives to induce an estrogenic response in patients. U.S. Pat. No. 2,751,313 discloses oral growth promoting compositions of several estrogenic agents and their use in promoting growth and increasing feed utilization efficiency in ruminant animals. U.S. Pat. No. 3,041,173 discloses the use of estrogenic agents in combination with other agents for enhancing growth in animals. U.S. Pat. No. 2,751,303 discloses the oral administration of estrogenic substances to promote growth in meat-producing animals. Useful estrogens include stilbestrol, 17.beta.-estradiol, derivatives of stilbestrol, estrone, dianisylhexene, genistein, dienstrol, and hexestrol. U.S. Pat. No. 3,235,454 discloses using long chain hydrocarbon aliphatic carboxylic acid esters of 17.beta.-estradiol for improving meat production in meat-producing animals. U.S. Pat. No. 3,729,560 discloses using estriol for treating hair and scalp. U.S. Pat. No. 3,166,473 discloses using esters of estriol for treating vaginitis, cervicitis, climacteric disturbance, menorrhagia and for shortening labor and facilitating delivery.
Estrogens such as 17.beta.-estradiol and diethylstibestrol are a group of biologically active compounds which are used in animals as growth promotants. In recent years, however, methods for promoting growth in animals, particularly ruminants such as sheep and cattle, using estrogens have been criticized because of the alleged adverse side effects caused by the compounds. These estrogenic compounds have been reported to induce excessive sexual stimulation of animals, including mammary development and lactation as well as other undesirable physiological side effects on the reproductive system. Methods for promoting growth and increasing feed utilization efficiency using new or known compounds which do not cause significant undesirable estrogenic side effects are therefore needed.